決まる and 決める: a settled schedule and a choice
Distinguish reporting a settled schedule from making a choice, and compare particles marking the decision and its outcome.
Announce what has been settled
旅行の日程が決まりました。 announces that the travel schedule has been settled. 決まる, read きまる, presents the result without identifying who had the authority to decide.
集合場所はまだ決まっていません。 says that the meeting place has not been decided yet. It does not also mean that the trip itself is cancelled.
The decision and its outcome
相談して、集合場所を決めました。 means that the group discussed and chose a meeting place. 決める, read きめる, presents the decision-makers' action with the place as its object.
In 集合場所を駅前に決めました。, the を phrase is what is being decided and 駅前に is the selected outcome. Both the decision item and its answer appear in one sentence.
Ask whether a choice has been made
In a restaurant, もう決まりましたか may ask whether you have chosen what to order. Use the setting and conversation to recover the omitted subject.
まだ迷っているので、先に決めてください。 means that the speaker is still undecided and asks the other person to choose first. 迷っている describes indecision; 決めて requests a choice.
What does 駅前に express in 集合場所を駅前に決めた?
Show the answer and why
It gives the selected meeting place. 集合場所を marks the decision item, and 駅前に tells us what was chosen for it.